Werner Lemberg writes: > On Sun, 2 Mar 1997, Hans Aberg wrote: > > > Actually, what is needed, is a simple extension of the TeX \def command: > > \def\name<parameter text>{definition text}[exception text] > > If a command somehow is unable to process the parameter text, then the > > original input text (before the parsing of the parameter text began) is > > left unaffected, and the execution passes to the exception text. > > Then stuff like optional commands could be implemented most easily, and > > perhaps the stuff you are asking for, too. > > This sounds for me like an OTP (Omega Translation Process) input filter. > With Omega you can do a lot of manipulation (notably character encoding > conversion and various more or less complicated character cluster->glyph > transformations e.g. for Hebrew or Arabic) of text before TeX sees the > text. You can avoid any active characters. i think you are mistaken. The comments by Hans are targeted towards general features or misfeatures (or missing features :-) of TeX's parsing machinery. OTPs in omega are filters which means they offer a preprocessing step but not a generally enhanced parsing functionality of the macro language itself. however as i said before this is not the right list to dicuss extensions to TeX itself frank